A recent study by the Rand Corporation indicated that methamphetamine (MA) abuse costs the United States over $20 billion/year. About 10 million Americans have used MA at least once. Chronic MA use has far reaching health consequences and a tremendous societal impact. At V.A. Medical Centers, abuse of MA is associated with increased use of other facility resources and deleterious consequences for veterans with additional psychiatric disorders. However, there are currently no approved medications for treatment of MA addiction, and consequently there is an urgent need to discover MA pharmacotherapies. MA is a substrate for the dopamine (DA) transporter (DAT) on DA neuron plasma membranes, and at intracellular vesicular monoamine transporters (VMAT2), and interferes with the physiological uptake and release of DA. The overarching goal of this proposal is to identify preclinical candidates, from a new and novel class of aryl piperidinequinazolinones (APQs). The novel compounds proposed here are designed to inhibit VMAT2 uptake and may utilize a new mechanism of action. In Specific Aim 1, identification of preclinical candidates will involve the sequential molecular modification of the lead compound APQs. Lead optimization will be achieved by sequential molecular modification and optimization of four regions of the parent compound with respect to inhibition of VMAT2 and selectivity versus competing biological targets that are identified using in vitro assays in Specific Aim 2. The in vitro assays include analysis of drug interactions with multiple binding sites on the VMAT2, VMAT2 function, effects on MA-induced changes in VAMT2 regulation, and drug interaction with other neurotransmitter receptors and transporters. Compounds will be modified to optimize electronic, steric and lipophilic factors on functional and inhibitory potency at VMAT2. Topological changes will be introduced to explore the three- dimensional requirement of VMAT2 inhibition. Bioenantioselectivity of the VMAT2 binding site will be exploited by design and evaluation of enantiopure compounds. In Specific Aim 3, selected lead compounds will be undergo behavioral pharmacological evaluation, including novel assays of MA effects developed in our laboratories, in addition to conventional assays of MA induced activity. This project has the potential to accelerate critical breakthroughs using an entirely new class of MA pharmacotherapies. It is unique in that it does not rely on the usual VMAT2 binding site for its functional effects and therefore affords an opportunity to construct molecules that differ in binding and pharmacological profiles from those already in exploration as anti-MA pharmacotherapies.